In general, an organic electroluminescence device (OLED) is one of flat plate display devices, and it is formed by interposing an organic thin film between an anode layer and a cathode layer on a wafer. The OLED is of a very thin matrix shape.
The OLED has many advantages in that it can be operated at a very low voltage and it is very thin. Thus, the OLED can solve the drawbacks of a conventional LCD including a narrow optical viewing angle, a low response speed, etc. In comparison with other types of displays, in particular, those of middles sizes, the OLED can provide the same image quality as that of, for example, a ‘TFT LCD’ or even higher ones than that. Furthermore, since the manufacturing process for the OLED is simple, the OLED has been attracting attention as the next-generation flat plate display device.
Referring to FIG. 1, there is illustrated a partial view of a conventional OLED.
As shown in the figure, the conventional OLED has a plurality of first electrodes 110 arranged in a parallel stripe pattern on a substrate 100 divided into a luminous portion A and a pad portion B. A multiplicity of second electrodes 120 is installed on the first electrodes 110 to be perpendicular thereto. Pixels 130 of the organic electroluminescence device are defined at intersecting areas of the first and the second electrodes 110 and 120, respectively, that are arranged orthogonally. Also, on every pixel 130, an organic thin film layer 140 including an organic emission layer is formed between the first electrodes 110 and the second electrodes 120.
Formed on the pad portion B of the substrate 100 are plural bus electrode patterns 150 and 160 connected to the second and the first electrodes 120 and 110, respectively. The bus electrode patterns 150 and 160 are typically formed together with the first electrodes 110, and they may be made of a transparent conductive material such as indium tin oxide (ITO), like the first electrodes 110. Further, auxiliary electrodes (not shown) made of chrome (Cr) or the like may be formed on a predetermined area of the first electrodes 110 to reduce the resistance thereof. In such a case, the bus electrode patterns 150 and 160 are formed together with the first electrodes 110 and the auxiliary electrodes, and thus ITO and Chrome (Cr) may be laminated in sequence. Further, though not shown in the drawing, a tape carrier package (TCP) is installed on the pad portion B such that it is electrically connected with the first electrodes 110, the second electrodes 120 and the bus electrode patterns 150 and 160. The TCP operates to apply electric signals to the pad portion B, thus driving the OLED.
It is well known in the art that, as the resistance of the bus electrode patterns 150 and 160 of the pad portion B decreases, a voltage drop due to the bus electrodes can be reduced when driving the OLED, which in turn allows a manufacture of a device featuring a low driving voltage and a low power consumption. For the reason, the resistance of the bus electrode patterns 150 and 160 needs to be reduced.